1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording for use to write data on a recording medium by means of a perpendicular magnetic recording system.
2. Description of the Related Art
The recording systems of magnetic read/write apparatuses include a longitudinal magnetic recording system in which the magnetization of signals is directed along the plane of a recording medium (the longitudinal direction), and a perpendicular magnetic recording system in which the magnetization of signals is directed perpendicular to the plane of a recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.
Magnetic heads for perpendicular magnetic recording typically have, like those for longitudinal magnetic recording, a structure in which a read head unit having a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head unit having an induction-type electromagnetic transducer for writing are stacked on a substrate. The write head unit includes a coil, a main pole and a return path section. The main pole has an end face located in a medium facing surface facing a recording medium. The coil produces a magnetic field corresponding to data to be written on the recording medium. The main pole passes a magnetic flux corresponding to the magnetic field produced by the coil, and produces a write magnetic field from its end face. The return path section is connected to the main pole. The return path section passes the magnetic flux corresponding to the magnetic field produced by the coil.
A magnetic head for use in a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface. The medium facing surface has an air inflow end (a leading end) and an air outflow end (a trailing end). An airflow that comes from the air inflow end into the space between the medium facing surface and the recording medium causes the slider to slightly fly over the surface of the recording medium.
Here, the side of the positions closer to the leading end relative to a reference position will be referred to as the leading side, and the side of the positions closer to the trailing end relative to the reference position will be referred to as the trailing side. The leading side is the rear side in the direction of travel of the recording medium relative to the slider. The trailing side is the front side in the direction of travel of the recording medium relative to the slider.
Magnetic heads for perpendicular magnetic recording are increasing in frequency of write signals to achieve higher recording densities. For such magnetic heads, it is thus required that the write current flowing through the coil should exhibit a rapid rise. To meet the requirement, it is effective to shorten the magnetic path through which the magnetic flux produced by the coil passes. To achieve this, reducing the number of turns of the coil is effective. However, a reduction in the number of turns of the coil would make the coil unable to provide a sufficiently large magnetomotive force.
Coils for use in magnetic heads for perpendicular magnetic recording are broadly classified into two types as follows. A first type is one that is wound around a portion of the return path section and not around the main pole. A second type is one that is wound around the main pole.
U.S. Pat. No. 8,810,963 B1 discloses a magnetic head including both of a coil of the first type and a coil of the second type. In this magnetic head, the coil of the first type and the coil of the second type are formed as completely separate coils. Further, in this magnetic head, a return path section is provided on the leading side of the main pole so as to define a space for respective portions of the coils of the first and second types to pass through. Since the space needs to be large, this magnetic head must disadvantageously include a long magnetic path formed by the main pole and the return path section which define the large space.